With Reddit Ads you can target a lot of different cities and regions, but you can’t always target what you want to. For example if your a service business in Orange County California you’ll quickly discover that you can’t target Orange County in the geo-targeting options. To target your ad correctly instead look for a sub-reddit that matches your target and select a geographic target that fits as well. In this example you could try geo-targeting California and targeting only users of the /r/orangecountry sub-reddit. Or you could try the sub-reddit’s of Anaheim, Irvine, and other cities located in Orange County.
Reddit Ads staffer MyNameIzKhan also recommended that advertisers could target a nearby area with the geo-targeting option, which in this case would be the city Los Angeles. Read this thread on the Reddit Advertising sub-reddit here.
Another plan would be to setup several different ad variations with different geographic / sub-reddit targeting options to see which one(s) work the best for you.